1. Field of the Invention
The present invention relates to a copy machine having a function for forming or writing special information upon copying a document image.
2. Description of the Prior Art
In JP-A No. 130782/1985, there is proposed an electrophotographic copy machine having a function capable of forming special information such as a page number, a date or the like upon copying a document image.
In this copy machine, a shutter means for shutting a light path of a document image toward a photoconductive drum and a data writing head comprising an LED array are provided and a desirable data such as a date is written on an area of the drum shaded by said shutter means upon copying a document image. Therefore, a copy of a document on which an image of the data is formed is obtained.
Further, a copy machine is provided having a duplex copy mode wherein first and second document images are copied on first and second sides of a copy sheet automatically and/or having a composite copy mode wherein first and second document images are copied on different areas of the same side of a copy sheet automatically.
In a copy machine having an information forming function together with the duplex copy mode and/or the composite copy mode, some inconveniences are caused as follows: In the duplex copy mode, the position of the information formed on the second side of a sheet seems unnatural when compared with that of the first side since the position is kept unchanged upon copying the second side although the relative position of the second document image in the sheet is changed with respect to the center line of the sheet, and in the composite copy mode, positions of information formed upon the first and second copying happen to be shifted with each other by a small distance since it is impossible to coincide the top position with each other exactly upon the first and second copyings.